The present invention relates to systems, devices and methods for data storage using optical media, and, more particularly, to storing information in structures, such as queues, using an optical medium.
Optical fibers have become key elements in data communication systems and networks when the data rate exceeds several tens of megabits per second or distances exceed several kilometers. As the demand for higher bandwidths continues, data communication systems and networks will be implemented increasingly using optical transmission techniques. This trend will be facilitated by the availability of components that store data using optically transmissive media. The operation of optical networks is described in Rajiv Ramaswarni and Kumar N. Sivarajan, xe2x80x9cOptical Networks: A Practical Perspective,xe2x80x9d (1998), which is incorporated herein in its entirety.
In an embodiment of the invention, data is stored as an optical signal in a loop formed from an optically transmissive medium. Data is inserted into the medium and data that has traversed the medium is reinserted into the medium. Additional data can be inserted into the loop in any order. Data stored in the loop can be rearranged or deleted. By controlling the manner in which data is stored in the loop, the loop can be made to operate as different types of storage, such as a first-in-first-out queue or random access storage. Amplification/regeneration of the optical signals is performed as needed to maintain the data in the loop.
In a further embodiment of the invention an initializing signal is inserted into a medium by an optical controller. The initializing signal may be an idle pattern or any other pattern that permits the optical controller to identify specific portions of the data stream in the optical signal traversing the medium. Once initialized, the system may be used to form one of a variety of data storage structures.
In another embodiment of the present invention, the controller forms a first-in-first-out queue in the medium by writing a start-of-queue marker and then an end-of-queue marker. Data is inserted into the queue by overwriting the end-of-queue marker and then writing the packet followed by a new end-of-queue marker. Data is removed from the queue by overwriting the start-of-queue marker and first packet with an idle pattern and then writing a new start-of-queue marker.
In a further embodiment of the invention, a controller initializes an optically transmissive medium by inserting a signal that divides the data stream in the medium into a plurality of sectors, with each sector a fixed length. Each of the sectors is characterized by a plurality of offset points for data in the sector. The controller both inserts data into the medium and reads data from the medium by selecting an offset point within a sector. This embodiment advantageously provides random access to the data stream in the optically transmissive medium.